Art of producing pigments by electrolysis.



No. 871,161. PATEN'IED NOV. 19, 1907.

E. D. GHAPLIN. ART OF PRODUCING PIGMENTS BY ELEGTROLYSIS.

grrmou on 11,111) mm, a, 1900.

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No. 871,161. 'PATENTED NOV. 19, 1907. E. D. GHAPLIN.

ART OF PRODUCING PIGMENTS BY ELEOTROLYSIS.

APPLICATION FILED FEB. a, 1906.

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' UNITED STATES. PATENT. oFnIo t EDWIN D. CHAPLIN, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO INTERNATIONAL LEAD COMPANIES, VOLUNTARY ASSOCIATION.

ART OF PRODUCING PIGMENTS BY ELECTROLYSIS.

Specification of Letters Patent.

Patented Nov. 19, 1907.

Application filed February 3. 1906. Serial No. 299.237,

To all whom it may concern:

Be it known that I, EDWIN D. OHAPLIN, a citizen of the United States, and a resident of Boston, in the county of Suffolk and State of Massachusetts, have invented a new and useful Improvement in the Art of Producing Pigments by Electrolysis, of which the following is a specification.

My invention relates to the art of producing pigments by electrolysis, and it relates more particularly to a process for so producing white lead or lead carbonate.

In the manufacture of lead carbonate by electrolysis, I prefer to employ an electrolyte which under the influence of the electric current will separate into a solvent of lead and an alkaline hydrate and thereby to produce in the anode compartment containing metallic lead, which may be the anode of the elec trolyzer, a solution of a soluble salt of lead, and in the cathode compartment, an alkaline hydrate. I have found it essential to the commercial production of white lead to maintain the lead solution and the alkaline hydrate separate and not to produce any lead precipitate in the electrolyzer itself. I have also found it essential to employ some means, such as an oxidizing agent, to re vent the formation of insoluble salts of ead in the electrolyzer.

As clearly set out in Letters Patent Nos. 555,232 dated February 25, 1896 and 563,553, dated July 7, 1896 granted to A. B. Browne and myself, and in Letters Patent No. 675,555 dated June 4, 1901 granted to G. Halloran and myself, certain insoluble basic salts of lead are formed in the electrolyzer, thereby rendering the processes uncommercial, unless certain precautions are taken in order to prevent such formation.

According to the process described Letters Patent No. 675,555, a soluble acid salt of lead is produced by forming from metallic lead as an anode a solution of a soluble salt thereof in the presence of a solublechlorid salt'and eventually carbonating the resulting lead oxychlorid. By these operations the formation of insoluble lead salts in the electrolyzer is prevented. In Letters Patent No. 563,553, the same result is accomplished, although not so perfectly, by the addition to the electrolyzer of an oxidizing agent, specified in the patent as nitric acid. In carrying out the process set forth in Letters Patent No. 675,555, the soluble chlorid salt probably is converted intoa soluble chlorate which operates in a manner analogous to the nitric acid em loyed in the process described-in the ear ier patent.

The object of the present invention is to provide'a'process of producing white lead by electrolysis in which the formation of insoluble salts of lead in the electrolyzer may be prevented by the use of a soluble chlorate salt which is added directly to the electro l te instead of being formed indirectly by e ectrolytic action from a soluble chlorid salt.

My invention may best be understood by having reference to the drawings which accompany and form a part of this specification, and which illustrate in diagrammatic form two arrangements of apparatus and circuits whereby m 1 process may be carried into effect; but it is to be understood that my invention is broader than'mere appara-. tus and may be carried into effect by a great variety of apparatus and merits. a

In the drawings, Figure 1 represents. an apparatus for carryingout my direct process for producing white ead and Fig. 2 represents an apparatus for carrying out my indirect process for producing white lead.

In Figs. 1 and 2, 1 represents a supplytank contaimng an electrolyte, which under the influence of the'electric current will be separated into an alkaline hydrate and a solvent of lead, such for example as an aqueous solution of a non-alkaline salt, preferably sodium nitrate, and containing also an a ueous solution of a soluble chlorate salt wiich may be a chlorate of an alkaline base, preferably sodium chlorate, or any other suitable chlorate salt. 1 w i I shall hereinafter refer to the solution in tank 1 as the neutral solution and shall assume that it consists of sodium nitrate and sodium chlorate. I

3 represents an electrolyzer divided into an anode compartment 3 and a cathode compartment 3",' by means of the foraminous diaphragms 4 4, between which is formed a circuit arrange I preferably by maintaining the level of the electrolyte between the diaphragms higher than the level of the anolyte and. catholyte. The level of the electrolyte in the compartment between the diaphragms is indicated by the dotted line 0, and the level of the anolyte and catholyte, which is governed by the height of the bends of the outlet pipes 7 and S, is indicated by the dotted lines 10, 10. In order to prevent said outlet pipes from siphoning the liquids out of the electrolyzer, the upper portion of each of said bends may be provided with an opening 26, 26 to equalize the atmospheric pressure on the columns of liquid in the two portions of each of said pipes.

The lead to be operated upon is placed in the anode conjipartment and may form the anode of the electrolyzer. In the present case the lead is shown in the form of a lead pig. 5, connected by the conductor (1 to the positive pole of the dynamo D, or other suitable source of current. The cathode of the electrolyzer 6 may consist of copper or any other suitable metal, and is connected by the conductor 5: to the negative pole of the dynamo.

\Vhen the electrolyzer is charged with the neutral solution and the electric current passed therethrough, a soluble acid salt of lead is formed in the anode compartment 3 and an alkaline hydrate, in the present case assumed above, sodium hydrate, is formed in the cathode compartment 3 Presumably lead nit-rate is at first formed in the anode compartment and this, by the continued action of the electric current, is

The term oxyc'hlorid of lead herein used.

has its usual meaningviz., chlorid salts of lead containing oxygen in varying proport1onssuch,- for instance as Pbcio,,Pbo.Pbc1,, 81 0.

According to the indirect process which may be carried out by the apparatus shown in Fig. 1, the solution of the acid salt of lead so formed in the anode compartment 3, is drawn off by the pipe 8 into the precipitating tank 15. The alkaline hydrate is drawn 0d by the pipe 7 into the tank 11, where it may be converted into an alkaline carbonate by subjecting it to the action of carbon dioxid which maybe formed in any suitable manner in the generator 12, and which may be conducted into the tank 11 by means of the pipe 18 provided with a Valve 13. The alkaline carbonate so formed is drawn off through the pipe 14, provided with the valve 14:, into the precipitating tank 15 Where it is mixed with the soluble lead salt and converts the latter into lead carbonate. The lead carbonate so formed settles upon the filter 16 at the bottom of the tank 15, while the filtrate which is substantially the original electrolyte, is pumped by the pump 26 through the pipe 17 provided with a valve thereby producing lead carbonate.

According to the indirect process which may be carried out by the apparatus-shown in F ig. 2, the solution of the aforesaid acid salt of lead may be discharged into the settling tank 20 by the pipe 8, and thence into the precipitating tank 22 by the pipe 21, which. is provided with the valve 21, or as is obvious, it may be discharged directly into said precipitating tank.

The alkaline hydrate produced in the oathode compartment 3" may be discharged into the settling tank 27 by the pipe 7 and thence into the precipitating tank 22 by the pipe 20 which is provided with the valve 20, or as is obvious, it may be discharged directly into said precipitating tank.

In the tank 22, lead hydrate is preci itated from the acid salt of lead and sett es on the filter 23 at the bottom of said tank while the filtrate, which in the present assumed case consists probably of a mixture .of sodium nitrate, sodium chlorate and sopipe 28 provided with the valve 28, and is.

converted into a bi-carbonate of an alkaline base,sodium bicarbonate in the present assumed vcase,by treating the same with carbon dioxid produced in the generator 12, which connects with the tank 11 by the pipe 13 provided with the valve 13.

The lead hydrate formed in the tank 22 is discharged by the pipe 24 provided with the valve 24 into the precipitating tank 15, and

the bicarbonate formed in the tank 11 is provided with the valve 14, thereby converting the lead hydrate into lead carbonate.

presence of a soluble chlorate salt, thereby,

' sald lead hydrate to produce lead carbonate.

:filtrate may be drawn off by the ipe 17.

By either the direct or the in irect process above described I am enabled, by the direct em loyment of a soluble chlorate salt, most e ectively to prevent the formation of insoluble basic salts of lead, the formation of which is fatal to a commercial production of white lead.- The process is continuous and, in addition to the lead and carbon dioxid consumed, re uires only the addition fromtime to time 0 fresh quantities of neutral solution.

I claim:

1. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically. dissolving metallic lead in an aqueous solution of a non-alkaline salt in the presence of a soluble chlorate salt and converting the resulting lead oxychlorid into lead carbonate.

2'. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically dissolving metallic lead in an aqueous solution of a non-alkaline salt in the producing an alkaline hydrate and lead oxychlorid, withdrawing and mixing said lead oxychlorid and said alkaline hydrate to precipitate lead hydrate, and then carbonating 3. As'an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically dissolving lead in an aqueous so lution of a non-alkaline salt in the presence of a soluble chlorate salt, thereby producing lead oxychlorid, withdrawing said lead oxychlorid and converting the same into lead hydrate and then carbonating said lead hydrate to produce lead carbonate.

4. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically dissolving lead in an aqueous solution of a non-alkaline salt in the presence of a soluble chlorate salt, thereby producing a solution of a soluble acid salt of lead, and then converting said soluble acid salt of lead into lead carbonate.

5. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically dissolving lead in an aqueous solution of a non-alkaline salt in the presence of a soluble chlorate salt, thereby producing an alkaline hydrate and a solution of soluble acid salt of lead, withdrawing and mixing said soluble acid salt of lead and said alkaline hydrate to precipitate lead hydrate and then carbonating said lead hydrate to produce lead carbonate.

6. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically dissolving lead in an aqueous so- 

